The present invention relates to a method and a device for safeguarding a hazardous working area of an automated machine. More particularly, the invention relates to a method and a device in which a respective current 3-D image of the working area is recorded and evaluated in order to avoid a risk to persons entering the working area.
Traditionally, the hazardous areas of automated machines are closed off with mechanical barriers in the form of protective fences and guard doors and using light barriers, light grids and laser scanners. As soon as a person opens a guard door or interrupts a light grid or a light barrier, a switch-off signal is generated and is used to stop the hazardous working movement of the machine. However, the installation of such protective devices is rather complicated and the protective devices require a large amount of space around a hazardous machine. In addition, such protective devices are not very flexible when it comes to adapting the safeguarding of the hazardous working area to different operating situations of the machine.
In order to avoid these disadvantages, efforts have been made for some time to safeguard the hazardous working area of an automated machine using camera systems and suitable image processing. US 2005/207618 A discloses such a system having at least two cameras which cyclically provide images of the hazardous working area. The images from the cameras are analyzed using at least two algorithmically different methods, and the hazardous working movement of the machine is stopped if at least one of the two methods detects a foreign object in a previously defined protection zone. Each of the two analysis methods generates 3-D information from the images of the cameras, with the result that the position of objects in the defined protection zone can be determined using the methods. A great challenge for such methods and devices is that the image processing, which is already complex anyway, must be fail-safe in terms of relevant machine safety standards, in particular EN 954-1 (already expired), EN ISO 13849-1 and IEC 61508, in order for such a device to be allowed for actual use safeguarding a hazardous machine. Failure of the device itself must not result in the safeguarding of the machine being lost. A device which achieves at least category 3 according to EN 954-1, SIL 2 according to IEC 61508 and/or performance level PL (d) according to EN ISO 13849 is therefore considered to be fail-safe in the following.
The method known from US 2005/207618 A and a corresponding device can achieve this and have already proved themselves in practical use. However, the known device has hitherto been able to detect only whether a foreign object is situated in a previously defined protection zone in order to slow down or stop a hazardous machine movement on the basis thereof. Man-machine interaction in the immediate vicinity of man and machine and flexible adaptation to changing operating situations and/or on the basis of the type of foreign object, are not readily possible with the known device. There is therefore a desire to further develop the known method and the corresponding device in order to enable, in particular, man-robot collaboration (human-robot interaction) inside the hazardous working area of a robot. For example, it is desirable for a person to be able to stay in the fundamentally hazardous working area of the robot while the robot is operating in order to monitor the machining processes of the robot in situ or to machine a workpiece at the same time or alternately with the robot. Nevertheless, it must still be ensured that the person is not injured by working movements of the robot.
DE 10 2007 007 576 A1 proposes a method and a device for safeguarding the hazardous working area of a robot, wherein a 3-D image of the working area is created and a kinematized human model is assigned to a person inside the working area. The 3-D image is analyzed in order to determine whether the actual state of the working area differs from a desired state of the working area, in which case the desired position of the person is taken into account using the kinematized human model. This method and the corresponding device are intended to enable man-robot collaboration. However, on account of the desired/actual comparison, a person in the working area of the robot must move in a manner exactly corresponding to the desired state in the kinematized human model. Corresponding modeling appears to be complicated and in any case limits flexibility since adaptation to new operating situations requires new modeling in each case. In addition, although DE 10 2007 007 576 A1 proposes the use of scanners as sensor units, which have single fail-safety according to category 3 of EN 954-1, cyclical or continuous checking of the functionality of the sensor units is also proposed and the movements of the robot during the checking phase are intended to be monitored using reliable technology, for example by redundantly detecting and evaluating the axial positions of the robot system. However, DE 10 2007 007 576 A1 does not contain any indication that the evaluation of the 3-D images and the underlying modeling can provide the fail-safety required for safeguarding hazardous working areas.
DE 10 2005 003 827 A1 discloses a similar device and a corresponding method for interaction between a person and a robot, wherein a model-based approach is also proposed here. The method described appears to be very computation-intensive and complex, and it is therefore doubtful whether the fail-safety and reaction speed required for the intended purpose can be achieved with modern computer performance.
DE 10 2009 031 804 A1 describes a method for detecting and tracking objects. DE 10 2006 048 166 A1 describes a method for observing a person in an industrial environment. In both cases, man-machine interaction is proposed as a possible field of application. However, none of the methods provides the fail-safety required for this intended purpose.
DE 20 2004 020 863 U1 describes a device for safeguarding a hazardous working area of a machine, the device comprising, on the one hand, light grids which detect when a person enters the working area with a high degree of fail-safety. The device also comprises a laser scanner which scans the working area behind the light grids in a horizontal plane. The laser scanner is designed to determine the position of a detected object. The light grids and the laser scanner are coupled in such a manner that the machine is stopped if a light grid has been interrupted and the laser scanner then does not detect a foreign object in a section of the working area which has been classified as less hazardous.